1. Field of the Invention
The present invention relates to an optical sensor device in which, an optical sensor element is mounted on a package material using a glass substrate.
2. Description of the Related Art
In recent years, mobile terminals such as mobile personal computers, tablet personal computers, and smartphones ere rapidly becoming widespread. This is because those mobile terminals have a large number of functions and another main reason is that they are designed to promote portability such as light in weight and thin in thickness. On the other hand, the number of electronic parts need in mobile terminals is numerous along with the pursuit of multi-functionality and portability, and further reduction in size, thickness, and cost and power saving are now always required. As a result, a resin mold package has been widely adopted for electronic parts. An optical sensor, which is one of electronic parts mounted in mobile terminals responsible for reducing power consumption is not exceptional. Similarly to other electronic parts, many products aimed at reducing the size, thickness, and cost by a resin mold package have been developed.
FIG. 6 is a cross-sectional view of an illuminance sensor package which is an electronic part disclosed in Japanese Published Patent Application No. 2007-36264 in which a light receiving element is mounted on an insinuating substrate made of a resin material and is molded by a resin. An electrode 22 is formed on the front surface of a resin substrate 20. The electrode 22 is wired so as to surround the rear surface of the substrate thereby being connectable to the outside. An electrode 23 has en optical sensor element 21 mounted thereon. A top surface 21a of the optical sensor element 21 and an electrode 24 are electrically connected via a wire 26. The optical sensor element 21 is firmly fixed onto the electrode 23 by a conductive paste 25. The conductive paste 25 electrically connects the optical sensor element 21 and the electrode 24 to each other.
In FIG. 6, the optical sensor element 21 is molded by a resin 2 as a whole. The resin 27 is made of a translucent resin, and an epoxy resin or the like is used. An infrared absorbing film 28 is provided on the resin 27. The infrared absorbing film 28 uses a resin and has a structure in which a liquid resin or a film, is adhered and laminated on the resin 27. As the liquid resin, an epoxy resin or the like is used. In the case of using a film, a film is adhered on the resin 2 via a resin adhesive. The optical sensor element 21 can thus receive visible light from which infrared tight has been filtered, thereby serving as an optical sensor corresponding to the visibility. Such infrared absorbing effect can also be obtained even when an infrared absorbing substance used for the infrared absorbing film 28 is dispersed and mixed in the translucent resin 27.
However, the optical sensor device described in Japanese Published Patent Application No. 2007-36264 has a package structure in which an epoxy resin or the like is need for sealing the element, and hence has a problem such as weak in environmental reliability including heat resistance and moisture resistance of the material. In particular, a resin or a film forcing the infrared absorbing film is thin and weak against heat and moisture.
Further, in the optical sensor device described in Japanese Published Patent Application No. 2007-36264, as the infrared absorbing film for obtaining intended characteristics a resin such as an epoxy resin is used as an example. In the case of using an epoxy resin or the like as the infrared absorbing film, the resin may be dissolved by moisture or heat. As a result, there is a problem that the infrared light as an absorption target cannot be absorbed and desired characteristics cannot be obtained progressively.
In light of the foregoing, some of electronic parts which use glass as a package material have been commercially available. The glass material prevents moisture and contaminants from entering from outside and is also high in airtightness. The glass material has a coefficient of thermal expansion approximate to that of a silicon substrate forming a semiconductor element, and hence when the semiconductor element is mounted on a glass package, the reliability of amounting surface or a bonding surface can be enhanced. In addition, the glass material is inexpensive, and hence the increase in manufacturing cost can be suppressed.
FIG. 7 is a cross-sectional view of an illuminance sensor package which is an electronic pert disclosed in Japanese Published Patent Application No. 61-214565 in which an optical sensor element is mounted on a substrate made of a ceramic material and is hermetically sealed by an insulating frame and a transparent glass plate. On the front and rear surfaces of a ceramic substrate 31, wiring patterns 32 and 39 are provided by metallization, respectively, and are electrically corrected to each other via a through electrode 38. An optical sensor element 33 is mounted on the substrate 31, and she top surface of the optical sensor element 33 and the wiring pattern 32 provided on the front surface of the substrate are electrically connected to each other via a wire 34. On the substrate 31, an insulating frame 35 is fixed via an adhesive 36 so as to surround the outside of the portion at which the wire 34 is connected to the wiring pattern 32. Transparent glass 37 is further adhered on the upper end of the insulating frame 35 by the adhesive 36.
The optical sensor element 33 is in a hollow state surrounded by the insulating frame 35 and the transparent glass 37. This is a structure in which the element and the wire are free from stress, which is often a problem to be solved in a structure sealed by a resin mold. External light enters the top surface of the optical sensor element 33 through the transparent glass 37 to generate an electro motive force. The electro motive force generated by the optical sensor element 33 is transferred from the wire 34 through the wiring pattern 32 and the through electrode 38 to a wiring pattern 39 provided on the rear surface side of the substrate 31. The substrate 31 is not a multilayer but a single layer of the ceramic material and, as the substrate material, a glass epoxy resin or the like is used as well as ceramic. Thus, the cost of the package is reduced.
The optical sensor device described in Japanese Published Patent Application No. 61-214565 does not use a resin which is used in the above-mentioned optical sensor device described in Japanese Published Patent Application No. 2007-36264, but mainly uses a high-reliability material such as ceramic and glass. This can eliminate a weak portion, which is a problem inherent in the resin material. However, the optical sensor device described in Japanese Published Patent application No. 61-214565 needs to be assembled with the use of different materials and parts such as the substrate, the insulating frame, and the transparent glass, and hence it is difficult to reduce the cost of the package. Further, the materials of the main components of the package, including the substrate, the insulating frame, and the transparent glass, have significantly different coefficients of expansion. Accordingly, under a temperature cycle test environment repeating high temperature and low temperature, the package is susceptible to damage due to stress generated by the difference in coefficient of expansion.
In the optical sensor device described in Japanese Published Patent application No. 61-214565, the optical sensor element 33 is surrounded by the insulating frame 35, and hence an area of the insulating frame 35 and further, a space for providing the through electrode 30 to the outside of the insulating frame 35 are required, causing a problem that reduction in size of the package is difficult.
FIG. 8 is a cross-sectional view of an optical semiconductor device which is an electronic part disclosed in Japanese Published Patent application No. 2006-13264 in which an optical semiconductor element is mounted on a ceramic substrate having a cavity and hermetically sealed with a transparent lid of glass or the like. A wiring conductor 42 and the cavity can be formed in a ceramic substrate 41 by laminating a green sheet punched in the shape of a frame, a green sheet having metal paste printed thereon, a green sheet having filled through-holes and the like. A transparent lid 45 has a plurality of holes 45a on the periphery thereof, and is bonded to the ceramic substrate 41 with a bonding agent 47 filled in the holes 45a. 
The optical semiconductor device described in Japanese Published Patent Application No. 2006-13264 does not nave an insulating frame as described in Japanese Published Patent Application No. 61-214565 and is formed of only ceramic and glass, and thus, high reliability is espoused. A ceramic substrate requires, however, a large number of steps such as punching and lamination of green sheets having metal paste printed thereon/fulfilled therein, and in addition, requires high heat treatment, which results in high manufacturing cost. Further, an area for the wiring conductor 42 is required to be secured, and thus, reduction in size of the package becomes difficult and the number of devices which can be produced in a batch becomes small, which cause a problem of further increase in the cost.